At this stage of the game, I can play in the upper octave easily, and with reasonable facility, but only if I play legato, that is, with open fingering.

If I try to move to the upper octave playing staccato, that is, with closed fingering, well, things don't go quite so well. I can sometimes get the upper octave note, but certainly not consistently, and moving to another upper octave note rarely works.

And so, these questions:

Is the upper octave typically easier to manage with open fingering? What might I work on to improve my upper octave success playing with closed fingering?

Sincere thanks for any insights, though good wishes, and prayers are certainly welcome,

Congratulations are in order for being able to play in the upper octave. I can't help too much with the closed fingering. For me it's just a case of finding whatever works best for the chanter - or rather conforming my technique to how my chanter wants to play. A great deal depends on fine control of bag pressure - it is always a case of finding just the right balance for your reed between pressure from the bag and back pressure within the chanter, as every note requires a slight adjustment.